A new economic study shows how your birth order can influence your career

For decades, psychologists and sociologists have studied the ways in which children’s birth order may affect their personalities. Perhaps surprisingly, economists are interested in that question too—particularly in terms of how birth order may influence the skills we develop in childhood, and the professional decisions we make later on.

In my new research with Erik Gronqvist and Bjorn Ockert, at the Institute for Evaluation of Labour Market and Education Policy in Sweden, we find that first-born children have a lot of advantages. My prior work using data from Norway has shown that, even within the same family, younger siblings have lower educational attainment, lower earnings, lower IQ, and generally worse health outcomes compared to their older siblings. Our new study finds that first-born kids also have the upper hand when it comes to personality characteristics and career achievements down the line.

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It’s tricky to isolate the effect of birth order. Because there is only a third-born child in a family with at least three children, for example, comparing third-borns to first-borns across families of different sizes will conflate the effect of the birth order of the child with the effect of the overall size of the family. There are also trends in outcomes over time that must be adjusted for—for example, we know educational attainment is increasing over time—and younger children are always born at a later time period. So we need large datasets to isolate the effects of birth order alone. One of the best places to look is Scandinavia, where the government keeps large administrative datasets.

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In our new study, to measure personality development, we use the outcome of a standardized psychological evaluation (conducted by a certified psychologist) performed on all Swedish men at around age 18 when they enlist in the military. Higher scores were assigned to those considered emotionally stable, persistent, socially outgoing, willing to assume responsibility, and able to take initiative. These evaluations are given in conjunction with standardized cognitive tests. The results? Later-born children had systematically lower scores on all these attributes.

Interestingly, we found that these personality differences translate into the types of jobs siblings take. First-born children are significantly more likely to be managers, while later-born children are more likely to be self-employed. More generally, first-born children are more likely to be in occupations with the highest requirements for sociability, leadership ability, conscientiousness, agreeableness, emotional stability, extraversion, and openness, including chief executives, legislators, and senior government officials. (Although our report focuses on men, we found similar patterns in occupational characteristics for women as well.)

Our new study finds that first-born kids also have the upper hand when it comes to personality characteristics and career achievements down the line.

The gender of the Swedish men’s older siblings also matters. A later-born boy with older brothers suffers almost twice as much in terms of these measured personality characteristics as a boy with older sisters. And when we look at whether an individual is working in what is considered to be a creative occupation, such as writers, musicians, and singers, boys are more likely to enter these occupations if they have older brothers than if they have older sisters.

There are many potential explanations for these patterns, ranging from biological differences by birth order to differences in sibling behavior to parents treating younger siblings differently. While it is hard to distinguish these, we think we’ve found some answers.

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Biology actually works against the patterns we see, as later-born children tend to have better birth outcomes as measured by factors such as birth weight—a standard proxy for health at birth. To more formally test the role of biology on these personality differences by birth order, we took advantage of the fact that some children’s biological birth order is different from their social birth order, due to the death of an older sibling or because their parent gave up a child for adoption. When we examine this subsample, we find that the birth order effect is entirely driven by the environmental factors.

When we look at explanations, we find that first-born teenagers are more likely to read books; spend more time on homework; and spend less time watching TV or playing video games. Parents also spend less time discussing school work with later-born children, suggesting there may be differences in parent’s time investments.

Overall, the study shows that younger children tend to have personality characteristics that lead to different career choices than their older siblings. They are less likely to be in higher-ranking positions (and earn less, as other research shows), as a result of their environment. And I don’t just say this because I am a first-born.